Which books refer on how archiect's manage to create neutral
architecture, when working in diverse communities with social and
ethnic division, i.e (in Berlin)?

There are plenty of books on Berlin's architecture; have a look at
this Amazon website -
http://www.amazon.com/exec/obidos/search-handle-form/103-5241996-1255061

Your question isn't very clear.  There has been a vast amount of
building there since the destruction of the Wall and the reunification
of the city; and many of the new buildings (eg Potsdamer Platz, the
restored Reichstag and the Chancellor's residence/offices) have been
in an ultra-modern International style. There has also been some very
careful restoration and adaptation of traditional buildings (eg
warehouses), especially in the former East German district of Mitte.
But I'm not sure the adjective "neutral" would apply to much of the
architecture.

Berlin isn't a particularly diverse community - eg compared with New
York, London or Toronto. There is a large Turkish community, but the
vast majority of Berliners are German.